The surface, cytoplasmic, and secreted immunoglobulin (Ig) of 8 human established lymphoid lines, grown from the peripheral blood of both healthy and diseased persons, were analyzed and compared. Surface Ig was found on every line; it was predominantly micron heavy chain and k light chain. Multiple heavy chain and light chain antigens were present for certain lines. Experimental results indicated the multiple chains were present on the same cells. Five of 8 lines had an excess of light to heavy chain. This excess was also present in some cases in cytoplasmic and secreted Ig. Comparison of secreted and cytoplasmic Ig antigens failed to reveal any cultured lines which lacked the ability to secrete synthesized Igs. Two lines with unusual findings were described. One had Ig antigens present in surface Ig but not in cytoplasmic Ig; the other showed the reverse situation. The cumulative data supported the value of established lymphoid lines in understanding the genetic control of human Ig at a cellular level.